The present invention relates generally to monitoring and controlling therapeutic beds and mattress systems. More particularly, the invention relates to a system and methods for detecting and monitoring the distance between a patient and a reference point on a mattress and for controlling the mattress in relation to such distance.
For years those who suffer from limited mobility due to age, disease or immobilizing physical condition have sought relief from decubitus ulcers, cramping and discomfort as a result of being bedridden for long periods of time. A wide range of therapeutic supports for bedridden patients, such as inflatable mattresses, mattress overlays and mattress replacements, have been made commercially available in the United States. One such support is commercially available from Kinetic Concepts, Inc. (of San Antonio, Tex.) under the xe2x80x9cTheraKairxe2x80x9d designation, as a mattress which provides pulsating action through inflatable support cushions as described in U.S. Pat. No. 5,267,364.
Therapeutic mattresses are often designed to reduce xe2x80x9cinterface pressures,xe2x80x9d which are the pressures that are exerted by a mattress on skin of the patient (or vice versa) while the patient is lying on the mattress. Given time, elevated interface pressures can reduce local blood circulation around the skin and, as a result, may contribute to bedsores and other complications. With inflatable mattresses, as the inflation air pressure decreases, a patient""s susceptibility to encountering elevated interface pressures also tends to decrease, thereby reducing the likelihood that the patient will develop bedsores.
A problem with deflation, however, is the increased risk of xe2x80x9cbottoming-outxe2x80x9d, which is a widely known effect where the upper surface of an air mattress converges and comes into direct contact with the lower surface. Bottoming out can negate much of the benefit of an air mattress by increasing the patient""s pressures at the point of bottoming-out and, therefore, increase the risk of bedsores. Abrupt bottoming-out, such as when the patient is initially positioned on the mattress, could increase the risk of further injury to an already frail, bedridden patient. There has been a long felt need to have an inflatable mattress which self-adjusts the air pressure in inflatable cushions for optimal therapeutic purposes while significantly diminishing the risks of bottoming-out.
Some concepts of regulating air supply within a mattress for the prevention of bedsores and some concepts for the mitigation of bottoming-out effects are known. For example, U.S. Pat. No. 4,694,520 describes methods for detecting inadequate inflation while the patient is situated on the mattress. By contrast, the present invention detects the patient not only when positioned on the bed but also before the patient is even placed on the bed, thereby preventing the risks of rapid bottoming-out by xe2x80x9cpre-inflatingxe2x80x9d.
U.S. Pat. No. 4,873,737 provides for the detection of mattress thickness to supply a mean air pressure while the patient is situated thereon.
U.S. Pat. Nos. 4,745,647 and 4,768,249 provide force activated sensors to detect whether a patient has bottomed-out on a mattress but does not contemplate detecting the patient as the patient nears the bed.
U.S. Pat. No. 4,542,547 provides for mattress inflation through the detection of reflected and pulsed light while the present invention, by contrast, detects diffuse light.
It is an object of the present invention to enhance patient care and to overcome the obstacles and inadequacies of the prior art.
The present invention includes features and/or components that have been invented or selected for their individual and combined benefits and superior performance as an apparatus and a method for minimizing patient interface pressures by sensing patient distance and, if necessary, adjusting that distance to some predetermined or calculated level to optimize the therapeutic effects of the patient""s mattress. The system is a combination of components and methods that together have new and novel features. Each of the individual components work in association with the others and are optimally mated for performances.
The present invention circumvents current laborious requirements of manually adjusting a mattress for optimal therapeutic inflation or allowing a patient to be filly positioned on the bed before sensing means are activated. The present invention offers a unique xe2x80x9chands-freexe2x80x9d approach to controlling a mattress""s air supply while a patient is lying thereon. Through the use of a heterodyning proximation detector similar benefits are achieved even before a patient lies upon the mattress. With such benefits there is less need for extra personnel and training costs to operate a mattress""s air supply system. In addition, the present invention further reduces any risks for rapidly bottoming-out as a patient is initially placed on a mattress. Accordingly, the heterodyning proximation detector detects a patient as the patient nears a mattress and allows for air supply in the mattress to be increased before the patient is ever positioned atop the mattress.
The heterodyning proximation detector is an improved version of a somewhat obscure musical instrument that had been developed in the United States during the 1920s called a xe2x80x9cThereminxe2x80x9d. The present invention improves on the musical instrument""s ability to sense a human""s natural reactance, or electrical characteristics, and applies this improvement to therapeutically regulating an air mattress. The heterodyning proximation detector is effectively an antenna referenced to a conducting plate with a large surface area that variably responds to the dielectric constants of different materials. The heterodyning proximation detector may also be used to control air supply while the patient is on the mattress along with, or separately from, a force-responsive distance sensing apparatus or a light-responsive distance sensing apparatus, thus reducing the risks for gradual bottoming-out as well.
Aspects of the present invention feature a force-responsive distance sensing apparatus for continuously determining how high the patient is being supported on the mattress in real-time while the patient is on the mattress. The depth that the patient sinks into the mattress is used for controlling air supply to the mattress. The patient""s height (or depth) distance is represented as variations in height of a compliant, force transmitting member that is placed relative to the mattress. Thus, a change in height of the patient generates a change of force applied to a force sensitive component coupled to the force transmitting member.
Other aspects of the present invention relate to a light-responsive distance sensing apparatus using either visible light or infrared radiation. The mattress upon which the patient rests may be physically divided into sections, such as independently inflatable air-cells, or logically divided into sections, where no physical barrier isolates the air inside the mattress. A section, logical or physical, of the mattress""s initial shape becomes deformed in response to a patient being set atop the air mattress. A light emitter and light detector are situated in a fashion such that a deformation in the mattress shape reduces the amount of light that reaches the detector from the emitter, thereby generating a control signal to adjust the air pressure within the mattress accordingly. The preferred embodiments contain certain elements which include, but are not limited to:
a frame for supporting a mattress;
a therapeutic mattress set upon the frame where both frame and mattress cooperate in tandem to define a therapeutic bed;
a controlled air supply for selectively inflating one or multiple air cells upon receiving data relating directly or indirectly to the height of the patient relative to the bottom of the air mattress.
In one preferred embodiment, a heterodyning proximation detector is significantly influenced by the reactance of certain objects within a known distance of the detector. Such an embodiment depends on the electrical signature left by the particular dielectric constant of that object and the field pattern of the heterodyning proximation detector. In particular, the heterodyning proximation detector is either a conducting plate or wire referenced to a ground plane that is responsive to a body""s natural reactance and, thus, functions as an antenna. The antenna is variably connected to a tank circuit having a capacitor and a variable inductor. A frequency oscillator is operatively connected to the tank circuit as well. Thus, as a body nears the antenna, the body""s reactance changes the electrical fields induced into the antenna, resulting in a change in the natural frequency of the oscillator. Accordingly, the frequency signal ultimately generated by the heterodyning proximation detector is used by control circuitry to create a signal which, in turn, controls a blower or regulating valve. The blower is then connected to at least one of the air cells or sections that comprise the mattress. Another embodiment of the apparatus contemplates an array of air cells each with a heterodyning proximation detector and a blower or regulating valve that is responsive to the individual reactance signatures emitted by particular segments of the body.
One embodiment includes a force-responsive distance sensing apparatus. The force-responsive distance sensing apparatus comprises a force transmitting member and a force sensing element, which might be a force-sensitive resistor, piezoelectric crystal, or the like, coupled with the force transmitting member. In operation, the force-responsive distance sensing apparatus is placed relative to the mattress so that it is responsive in real-time to the compressive forces that are continuously generated by the patient when the patient is on the mattress. When a patient lying on the mattress has compressed it to the point of bottoming, the force transmitting member is subjected to the maximum amount of loading that is exerted by the patient on the mattress, whereas an uncompressed, fully inflated mattress signifies minimum or no loading on the force transmitting member. In turn, a force sensing element that is coupled to the force transmitting member detects a range of height distance in real-time as a variable range of compression exerted thereon by the force transmitting member. However, compression of the force transmitting member is not necessarily linearly scaled between the maximum and minimum distances of the patient relative to frame; e.g., compressive forces from the force transmitting member might not be generated until the mattress thickness is compressed to some predetermined ratio of the original thickness.
Ultimately, a resulting signal from the force sensing element that is related to the compressive forces exerted on the element of the force transmitting member is sent to a controller and compared to a preset calibrating signal. The signal is then converted into a control signal which is sent to a blower or regulating valve. The controller might also be set to work with a microprocessor to store and compare various voltage values.
One embodiment includes a light-responsive distance sensing apparatus. The light-responsive distance sensing apparatus comprises a deformable container, inflatable chamber, or the like, having a sealed inner surface that is constructed of light diffusing material. A light emitter and a light detector are attached to the air cell at different locations. In operation, as a patient is set atop the air mattress, the initial shape of the air cell becomes deformed due to the compressive forces exerted by the patient thereon. Thus, any deformation of the container""s inner surface between the light emitter and light detector would scatter light so that, ultimately, less light would be received and detected by the light detector than what light was initially emitted when the air cell was not subject to compressive forces. The resulting output signal from the light detector is sent to a controller and compared to a calibrated reference signal. The controller may then emit a control signal that indicates a significant disparity in the air supply within that air cell or mattress section to a blower or regulating valve to increase air supply.
One particular embodiment provides a therapeutic mattress for controlled support of a patient, the mattress comprising at least one inflatable chamber having a first translucent portion for the introduction thereto of light energy and a second translucent portion for the passage therethrough of light energy; a source of light energy adapted to introduce light energy through the first translucent portion into the interior of the inflatable chamber; and a receiver of light energy adapted to receive light energy through the second translucent portion from the interior of the inflatable chamber, the receiver being adapted to generate a signal indicative of the quantity of light so received. The first and second translucent portions are preferably disposed on opposing sides of the inflatable chamber. The inflatable chamber also has one or more pouches to secure the source and/or the receiver to the chamber. Preferably, the pouch also has a releasable closing to facilitate insertion and removal of the source and/or receiver. The pouch optionally also has an opaque portion to conceal the source and/or receiver secured within the pouch and a reflective portion to facilitate the transfer of light energy through the chamber. Cushioning material, such as foam, plastic, or cloth batting, is optionally disposed within the inflatable chamber to provide extra support cushioning to the patient. The chamber optionally also includes an air permeable portion to facilitate a gradual flow of air out of the chamber, and a water permeable portion to draw moisture away from the patient.
Another embodiment provides a therapeutic mattress for controlled support of a patient, the mattress comprising a plurality of inflatable chambers each having a light-scattering inner surface; a first of the inflatable chambers having a first light emitter and a first light detector; a second of the inflatable chambers having a second light emitter and a second light detector; and first and second pouches adjacent opposite sides of each of the first and second inflatable chambers. The first light emitter is disposed within the first pouch of the first chamber and is adapted to introduce light energy, preferably infrared light, into the interior of the first chamber. The first light detector is disposed within the second pouch of the first chamber and is adapted to receive light energy from the interior of the first chamber and generate a signal indicative of the quantity of light energy received. The second light emitter is disposed within the first pouch of the second chamber and is adapted to introduce light energy into the interior of the second chamber. The second light detector is disposed within the second pouch of the second chamber and is adapted to receive light energy from the interior of the second chamber and generate a signal indicative of the quantity of light energy received. Furthermore, the mattress is provided with a source of pressurized fluid in communication with the first and second inflatable chambers, the source being adapted to control inflation of the first chamber according to the signal generated by the first light detector, the source being further adapted to control inflation of the second chamber according to the signal generated by the second light detector. Inflation of the first and second inflatable chambers is controlled to minimize interface pressures between the therapeutic mattress and a patient lying on the mattress while simultaneously maintaining sufficient air pressure to prevent the inflatable chambers form bottoming out.
Other embodiments may include other distance sensing mechanisms either alone or in combination with the heterodyning proximation detector, force-responsive distance sensing apparatus or the light-responsive distance sensing apparatus, adapted to assist in controlling and monitoring the air supply of the mattress.
The invention may take the form of a method for regulating inflation within a mattress assembly or overlay. Such a method can be used to better accommodate a wide range of patient body sizes. The preferred method includes the following steps:
1. deflating the mattress and measuring and storing the height distance from a heterodyning proximation detector to a patient while the mattress is deflated;
2. initiating inflation of the mattress as the patient nears the heterodyning proximation detector;
3. placing the patient on the mattress and continuing to increase the air supply of the mattress until fully inflated.
4. measuring and storing the output signal or signals from the heterodyning proximation detector, force-responsive distance sensing apparatus, light-responsive distance sensing apparatus, or any combination of these while the mattress is fully inflated with a patient on top of the mattress;
5. calibrating the optimal height distance for that particular patient using the stored signals from the deflated and fully inflated positions;
6. monitoring and controlling air supply to the mattress based on the determined optimal height distance using the heterodyning proximation detector, force-responsive distance sensing apparatus, light-responsive distance sensing apparatus, or any combination of these.
Among those benefits and improvements that have been disclosed, other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings. The drawings constitute part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.